The mayor's office announced that Clement, the deputy mayor for government and external relations, resigned earlier today following the discovery of further "discrepancies" less than a week after published receipts detailed how Clement had used the card for personal items over a matter of months.

The exact nature of the "discrepancies" have not been made public. But it emerged separately that Clement claimed money back for a business dinner on 5 November 2008 with the Tory leader of Barnet council, Mike Freer, which appears not to have taken place.

Freer's office issued a brief statement today to confirm that on the day in question he was at a funeral in Inverness.

Clement's departure brings to three the number of deputy mayors who have resigned or been forced to quit since Johnson came to office in May 2008, alongside two other mayoral appointments.

Today's revelations are particularly embarrassing since Johnson came to office on a promise to clean up the mayoral regime, cut waste and deliver value for taxpayers' money.